#include "../inc/md5.h"

/*
 * Constants for MD5Transform routine.
 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

#define LENGTH 16

static unsigned char PADDING[64] =
{
    0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
 * F, G, H and I are basic MD5 functions.
 */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/*
 * ROTATE_LEFT rotates x left n bits.
 */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/*
 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. Rotation is
 * separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) { \
        (a) += F ((b), (c), (d)) + (x) + (unsigned)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
    }
#define GG(a, b, c, d, x, s, ac) { \
        (a) += G ((b), (c), (d)) + (x) + (unsigned)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
    }
#define HH(a, b, c, d, x, s, ac) { \
        (a) += H ((b), (c), (d)) + (x) + (unsigned)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
    }
#define II(a, b, c, d, x, s, ac) { \
        (a) += I ((b), (c), (d)) + (x) + (unsigned)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
    }

/*
 * Encodes input (unsigned) into output (unsigned char). Assumes len is a
 * multiple of 4.
 */
static void Encode(unsigned char *output, unsigned *input, unsigned int len)
{
    unsigned int    i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
    {
        output[j] = (unsigned char)(input[i] & 0xff);
        output[j + 1] = (unsigned char)((input[i] >> 8) & 0xff);
        output[j + 2] = (unsigned char)((input[i] >> 16) & 0xff);
        output[j + 3] = (unsigned char)((input[i] >> 24) & 0xff);
    }
}

/*
 * Decodes input (unsigned char) into output (unsigned). Assumes len is a
 * multiple of 4.
 */
static void Decode(unsigned *output, unsigned char const *input, unsigned int len)
{
    unsigned int    i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((unsigned) input[j]) | (((unsigned) input[j + 1]) << 8) |
                    (((unsigned) input[j + 2]) << 16) | (((unsigned) input[j + 3]) << 24);
}

/*
 * MD5 basic transformation. Transforms state based on block.
 */
static void MD5Transform(unsigned state[4], const unsigned char block[64])
{
    unsigned a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    Decode(x, block, 64);
    /* Round 1 */
    FF(a, b, c, d, x[0], S11, 0xd76aa478);  /* 1 */
    FF(d, a, b, c, x[1], S12, 0xe8c7b756);  /* 2 */
    FF(c, d, a, b, x[2], S13, 0x242070db);  /* 3 */
    FF(b, c, d, a, x[3], S14, 0xc1bdceee);  /* 4 */
    FF(a, b, c, d, x[4], S11, 0xf57c0faf);  /* 5 */
    FF(d, a, b, c, x[5], S12, 0x4787c62a);  /* 6 */
    FF(c, d, a, b, x[6], S13, 0xa8304613);  /* 7 */
    FF(b, c, d, a, x[7], S14, 0xfd469501);  /* 8 */
    FF(a, b, c, d, x[8], S11, 0x698098d8);  /* 9 */
    FF(d, a, b, c, x[9], S12, 0x8b44f7af);  /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
    /* Round 2 */
    GG(a, b, c, d, x[1], S21, 0xf61e2562);  /* 17 */
    GG(d, a, b, c, x[6], S22, 0xc040b340);  /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa);  /* 20 */
    GG(a, b, c, d, x[5], S21, 0xd62f105d);  /* 21 */
    GG(d, a, b, c, x[10], S22, 0x2441453);  /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8);  /* 24 */
    GG(a, b, c, d, x[9], S21, 0x21e1cde6);  /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[3], S23, 0xf4d50d87);  /* 27 */
    GG(b, c, d, a, x[8], S24, 0x455a14ed);  /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[2], S22, 0xfcefa3f8);  /* 30 */
    GG(c, d, a, b, x[7], S23, 0x676f02d9);  /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
    /* Round 3 */
    HH(a, b, c, d, x[5], S31, 0xfffa3942);  /* 33 */
    HH(d, a, b, c, x[8], S32, 0x8771f681);  /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[1], S31, 0xa4beea44);  /* 37 */
    HH(d, a, b, c, x[4], S32, 0x4bdecfa9);  /* 38 */
    HH(c, d, a, b, x[7], S33, 0xf6bb4b60);  /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[0], S32, 0xeaa127fa);  /* 42 */
    HH(c, d, a, b, x[3], S33, 0xd4ef3085);  /* 43 */
    HH(b, c, d, a, x[6], S34, 0x4881d05);   /* 44 */
    HH(a, b, c, d, x[9], S31, 0xd9d4d039);  /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[2], S34, 0xc4ac5665);  /* 48 */
    /* Round 4 */
    II(a, b, c, d, x[0], S41, 0xf4292244);  /* 49 */
    II(d, a, b, c, x[7], S42, 0x432aff97);  /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[5], S44, 0xfc93a039);  /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[3], S42, 0x8f0ccc92);  /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[1], S44, 0x85845dd1);  /* 56 */
    II(a, b, c, d, x[8], S41, 0x6fa87e4f);  /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[6], S43, 0xa3014314);  /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[4], S41, 0xf7537e82);  /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[2], S43, 0x2ad7d2bb);  /* 63 */
    II(b, c, d, a, x[9], S44, 0xeb86d391);  /* 64 */
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
    /*
     * Zeroize sensitive information.
     */
    memset((unsigned char *) x, 0, sizeof(x));
}

/**
 * MD5Init:
 * @context: MD5 context to be initialized.
 *
 * Initializes MD5 context for the start of message digest computation.
 **/
void MD5Init(MD5_CTX *context)
{
    context->count[0] = context->count[1] = 0;
    /* Load magic initialization constants.  */
    context->state[0] = 0x67452301;
    context->state[1] = 0xefcdab89;
    context->state[2] = 0x98badcfe;
    context->state[3] = 0x10325476;
}

/**
 * MD5Update:
 * @context: MD5 context to be updated.
 * @input: pointer to data to be fed into MD5 algorithm.
 * @inputLen: size of @input data in bytes.
 *
 * MD5 block update operation. Continues an MD5 message-digest operation,
 * processing another message block, and updating the context.
 **/

void MD5Update(MD5_CTX *context, const unsigned char *input, unsigned int inputLen)
{
    unsigned int    i, index, partLen;
    /* Compute number of bytes mod 64 */
    index = (unsigned int)((context->count[0] >> 3) & 0x3F);

    /* Update number of bits */
    if ((context->count[0] += ((unsigned) inputLen << 3)) < ((unsigned) inputLen << 3))
    {
        context->count[1]++;
    }

    context->count[1] += ((unsigned) inputLen >> 29);
    partLen = 64 - index;

    /* Transform as many times as possible.  */
    if (inputLen >= partLen)
    {
        memcpy((unsigned char *) & context->buffer[index], (unsigned char *) input, partLen);
        MD5Transform(context->state, context->buffer);

        for (i = partLen; i + 63 < inputLen; i += 64)
        {
            MD5Transform(context->state, &input[i]);
        }

        index = 0;
    }
    else
    {
        i = 0;
    }

    /* Buffer remaining input */
    if ((inputLen - i) != 0)
    {
        memcpy((unsigned char *) & context->buffer[index], (unsigned char *) & input[i], inputLen - i);
    }
}

/**
 * MD5Final:
 * @digest: 16-byte buffer to write MD5 checksum.
 * @context: MD5 context to be finalized.
 *
 * Ends an MD5 message-digest operation, writing the the message
 * digest and zeroing the context.  The context must be initialized
 * with MD5Init() before being used for other MD5 checksum calculations.
 **/

void MD5Final(unsigned char digest[16], MD5_CTX *context)
{
    unsigned char   bits[8];
    unsigned int    index, padLen;
    /* Save number of bits */
    Encode(bits, context->count, 8);
    /*
     * Pad out to 56 mod 64.
     */
    index = (unsigned int)((context->count[0] >> 3) & 0x3f);
    padLen = (index < 56) ? (56 - index) : (120 - index);
    MD5Update(context, PADDING, padLen);
    /* Append length (before padding) */
    MD5Update(context, bits, 8);
    /* Store state in digest */
    Encode(digest, context->state, 16);
    /*
     * Zeroize sensitive information.
     */
    memset((unsigned char *) context, 0, sizeof(*context));
}

char *MD5End(MD5_CTX *ctx, char *buf)
{
    int i;
    unsigned char digest[LENGTH];
    static const char hex[] = "0123456789abcdef";

    if (!buf)
    {
        buf = (char *)malloc(2 * LENGTH + 1);
    }

    if (!buf)
    {
        return 0;
    }

    MD5Final(digest, ctx);

    for (i = 0; i < LENGTH; i++)
    {
        buf[i + i] = hex[digest[i] >> 4];
        buf[i + i + 1] = hex[digest[i] & 0x0f];
    }

    buf[i + i] = '\0';
    return buf;
}

char *MD5Data(const unsigned char *data, unsigned int len, char *buf)
{
    MD5_CTX ctx;
    MD5Init(&ctx);
    MD5Update(&ctx, data, len);
    return MD5End(&ctx, buf);
}

